1. Field of the Invention
The present invention relates to an aligned single-walled carbon nanotube aggregate, a bulk aligned single-walled carbon nanotube aggregate, and a powdered aligned single-walled carbon nanotube aggregate and, more specifically, it relates to an aligned single-walled carbon nanotube aggregate, a bulk aligned single-walled carbon nanotube aggregate, and a powdered aligned single-walled carbon nanotube aggregate, not available until now, possessing high purity, high specific surface area, able to be produced in large scale and in patterns.
2. Description of the Related Art
In recent years, development of carbon nanotubes (CNTs) has been expected for new functional materials such as new electronic device materials, optical device materials, conductive materials, and bio-related materials, and studies have been progressed earnestly for application use, quality, mass productivity, etc.
Among CNTs, single-walled CNTs have attracted attention as a material for nano-electronic devices, nano-optical devices, and energy storage devices since they are extremely excellent in electrical property (extremely high current density), thermal property (heat conductivity comparable with diamond), optical property (light emission in an optical communication band wavelength region), hydrogen storing performance, and metal catalyst supporting performance as well as have both properties of semiconductors and metals.
In a case of effectively utilizing the single-walled CNTs for the application uses described above, it is desired that a plurality of single-walled CNTs form a bundle, film, or aggregate gathered in a specified direction and the single-walled CNT aggregate provides electric or electronic, and optical functionality. Further, it is desired that the length (height) of the single-walled CNT aggregate is larger. It is expected that the application field of CNT is greatly extended when such aligned single-walled CNT aggregate is created.
On the other hand, one of methods for producing CNT, a chemical vapor deposition method (hereinafter also referred to as a CVD method) has been known (refer, for example, to JP-A-2003-171108). The method has a feature of bringing a carbon compound into contact with fine metal particles as a catalyst in an atmosphere at a high temperature of about 500° C. to 1,000° C. and CNTs can be produced while variously changing the kind and the arrangement of the catalyst, kind of carbon compounds, and reaction conditions, and it has attracted attention as being suitable to mass production of CNTs. Further, the CVD method has an advantage capable of producing both single-walled carbon nanotube (SWCNT) and multi-walled carbon nanotube (MWCNT) and capable of producing a number of CNTs aligned vertically to the surface of a substrate by using a substrate supporting the catalyst.
The aligned CNT aggregate having a high specific surface area, alignment property, and having moldability to various forms and shapes is extremely suitable as substance—energy storage materials in various application uses such as electrodes for super capacitors and heat conducting and heat dissipating materials having directional anisotropy, but such CNT aggregate has yet not been obtained so far.
Since the existent CNT aggregates are a one-dimensional elongate flexible material with extremely high aspect ratio and tend to adhere to each other due to a strong Van der Waals force, they tend to form a disordered and not-aligned aggregate with a low specific surface area. Then, since it is extremely difficult to re-constitute the alignment property of the once disordered and not-aligned aggregate, it was difficult to produce an aligned CNT aggregate of high specific surface area having moldability.
In view of the problems in the prior art described above, the present invention mainly intends to provide an aligned single-walled CNT aggregate, a bulk aligned single-walled CNT aggregate, and an powdered aligned single-walled CNT aggregate which can be produced easily and has a high specific surface area, in which individual CNTs are aligned in an orderly direction and which has moldability due to low bulk density. “Aligned single-walled CNT aggregate” referred to in the present specification means a aggregate of a plurality of single-walled CNTs grown to a predetermined direction from a substrate used for growth, “bulk aligned single-walled CNT aggregate” means an object obtained by peeling the aligned single-walled CNT aggregates together from a substrate, and “powdered aligned single-walled CNT aggregate” means an object obtained by peeling the aligned single-walled CNT aggregates from the substrate into a powder form.